1. Field of the Invention
This invention relates to a valve device for controlling liquid flow, in particular for use in filling a carton.
2. Description of the Prior Art
European Patent Publication No. 0013132 discloses an aseptic packaging machine which includes a chain conveyor conveying cartons along a path in an aseptic chamber including an advance leg and a return leg each extending along the machine. Ultra-violet germicidal lamps extend over at least a major portion of the advance leg. Aseptic liquid is fed into the cartons by a filling device. After filling, the cartons are top-heated and sealed by a top-heating device and a top-sealing device. The only non-aseptic matter deliberately introduced into the chamber is the cartons. The chamber is cleaned internally by cleaning fluid from spray nozzles. The carton entry to and exit from the chamber have aseptic air curtains.
The filling device is particularly designed to prevent microbes obtaining access to the aseptic liquid product being supplied to the aseptic chamber. The filling device includes a mounting frame which mounts four stainless steel reciprocatory bellows having bottom walls which are reciprocatorally driven by respective reciprocatory plungers and having top flanges fixed to respective lower limbs of fixed T-unions. Respective upper limbs of the unions contain respective spring-loaded, non-return, inlet valves which open to allow downward flow through the limbs. Intermediate limbs of the respective unions are connected to respective arcuate pipes which curve downwardly towards the path of the cartons and which at their lower ends are connected to respective outlet nozzles which contain respective spring-loaded, non-return, outlet valves. The chains advance the cartons stepwise directly below the line of nozzles and a selected number of the bellows are operated each to deliver a predetermined dosage of long-life milk to the vertically upright cartons, the number of bellows operated being dependent upon the nominal capacity of the cartons. Thus, with each bellows being pre-set to deliver a half pint at each reciprocation, all four bellows are operated for cartons which can each hold one quart. On each bellows performing a pressure stroke, because the inlet valve in its union is held closed by its spring and by the milk pressure, the inlet valve is automatically opened against the action of its spring so that the bellows can draw in milk from an expansion chamber.
In a widely used design applicable to that machine, the nozzle would comprise a tubular housing and a valve member in the housing. The tubular housing is formed internally, at a location spaced an appreciable distance above its lower extremity, with a valve seat in the form of a downwardly-facing, frusto-conical surface. Immediately beyond this surface, the housing widens to form an expansion space and then narrows again to continue downwards as a cylindrical bore. The valve member comprises a disc-form driving part, a stem extending downwards from the driving part, and a closure part fixed to the lower end of the stem and having a frusto-conical surface co-axial with the housing and arranged to come face-to-face with the valve seat. This latter surface is formed with a co-axial annular groove containing an elastomeric O-ring for sealing against the valve seat. The valve member is movable axially between a closed condition in which the closure part is within the tubular housing and acts sealingly on the valve seat by way of the O-ring and an open condition in which the closure part is still within the housing but spaced downwards from the valve seat. The valve member is encircled by a closing spring urging the closure part into its closed position. The driving part is a downwardly diverging, frusto-conical disc co-axial with the housing, which has a downwardly diverging, frusto-conical, internal surface encircling the disc and of a cone angle equal to that of the disc. In the closed condition of the valve member, there is a very small clearance between the disc and this surface. The valve member is opened by the pressure differential between the pressure of the liquid upstream of the driving part and the pressure downstream of the driving part. When this pressure differential is sufficiently high to overcome the pressure of the spring, the valve member opens. As the valve member opens, the clearance width between the driving part and its complementary surface of the housing increases linearly. The driving part is considerably smaller in diameter than is the O-ring. The extent of compression of the spring determines the extent of opening of the valve member. The valve member includes a second stem extending downwardly from the closure part and widening at its lower end region to obturate the cylindrical bore in the closed condition of the valve member. In the open condition, the lower extremity of this stem is spaced downwards from the housing and the liquid can flow down therebetween. The valve member also includes two or more fins which extend upwardly from the lower end of the second stem and slide on the surface of the cylindrical bore. Were it not for the fins, in the open condition of the valve member, the liquid would flow from the valve member as a substantially unbroken tube of liquid. This would mean that air trapped within the tube of liquid and increasingly under pressure as the liquid level in the carton climbs would be forced to break through the tube of liquid to escape and in so doing would disturb the smooth flow of the liquid into the carton and cause splashing of liquid beyond the carton. The presence of the fins ensures that corresponding vents are formed along the tube of liquid through which vents air can flow without disturbing the flow of the liquid.
The nozzle described above has a number of disadvantages.
The extent of opening of the valve member is relatively unpredictable, because the clearance width between the driving part and its complementary surface of the housing increases continuously from the closed condition to the maximum open condition, so that the open position of the driving part can be almost anywhere along such complementary surface, depending upon the pressure differential upon the driving part, which itself depends upon the velocity and viscosity of the liquid. Such unpredictability can lead to difficulties in designing and operating the machine to cope with various liquids and various containers, particularly since there is an optimum range of rate of flow of liquid into the carton. Another disadvantage is that, as the valve member reaches its closed condition under the action of the return spring its speed is relatively high and the closure part strikes the valve seat at speed, causing liquid at the valve seat to be spat out in various directions. In addition, the housing has an appreciable area of its internal surface below the annulus of sealing between the valve seat and the O-ring, and this area is normally wetted by contact with the liquid from the open outlet valve, so that there is a risk that liquid will drip from the nozzle even when the outlet valve has been fully closed and thus drip onto the exteriors of cartons or onto the conveyor forwarding the cartons. Such dripping is obviously undesirable.
U.S. Pat. No. 2,962,227 discloses a fuel injection nozzle comprising a tubular body internally screwthreaded to receive a connector nipple having an internal bore terminating at its lower end in a cylindrical chamber. Located in the chamber is a detachable tubular valve housing through which extends a stem carrying at its lower end a valve closure member of apparently frusto-conical form co-operating with an apparently frusto-conical valve seat within the outlet of the housing. The upper end of the stem is externally screwthreaded to receive an internally screwthreaded metal disc formed with angularly drilled apertures each inclined inwardly and downwardly and having its lower end spaced from the stem. These apertures permit fuel to pass to beneath the disc. The valve stem is maintained in position on the disc by a lock nut. The central bore of the valve housing is counterbored to receive a distance piece and a helical spring bearing at its lower end on the distance piece and at its upper end against the underside of the disc. In the bottom of the chamber and underneath the disc is a ring of elastomeric material which is normally separated from the underside of the disc by a small free space. When the nozzle is operated at low delivery rates, fuel enters the chamber and passes through the apertures in the disc and down to the valve seat. The fuel pressure thereby built up downstream of the disc ultimately forces the valve closure member to open against the force of the spring, so that the fuel is injected, but a small free space still remains between the elastomeric ring and the disc. However, at high delivery rates, the valve opens more, thus pressing the disc against the ring and thereby closing the free space. Thereupon, less of the underside of the disc is exposed to the fuel pressure, so that the valve is maintained more reliably in that position.
The fuel injection nozzle just described is clearly not designed for use with liquids of a relatively wide range of viscosities, since the higher the viscosity of the liquid, the greater would be the tendency for the disc to contact the ring at relatively low delivery rates. Furthermore, if an enlarged such nozzle were to be used in the filling of cartons, as the wetted, apparently frusto-conical surfaces of the valve closure member and the valve seat came together as the valve closure member reached its closed position, they would squeeze out downwardly from between them drops of liquid which would be liable to drop onto the cartons or the machine parts below them. A further disadvantage would be that the issuing of liquid from immediately adjacent to the lower end of the housing, which would occur irrespective of the extent of opening of the valve member, would mean that a container conveyed along sideways to immediately beneath the housing would be likely to have liquid splashed onto any top sealing surfaces thereof and over onto the outside of the container, which would obviously be disadvantageous.